This project provides measurements and statistical analyses of epidemiological, environmental, and photobiologic data relevant to the etiology of skin cancer, including malignant melanoma. Through these studies, NCI provides research in response to Public Law 95- 95 (Amendment to the Clean Air Act) and the Federal stratospheric ozone protection policy program. A new international agreement calls for a worldwide limitation and eventual freezing of chlorofluorocarbon production, which has been linked to recent stratospheric ozone depletions. However, anticipated concomitant increases in solar ultraviolet of wavelengths from 290 to 330 nm (ultraviolet) which would cause increases in skin cancer incidence, including melanoma, were not observed in eight geographic areas of the United States from 1974 to 1985. Detailed time series summaries of daily, monthly and annual amounts of UVB from these and other NCI incidence survey locations are being utilized to refine our dose-response estimates, and to provide comparisons with surface and stratospheric measurements of ozone and other meteorological factors (e.g., UVB-absorbing aerosols) which may clarify apparent discrepancies in trends. Adjusting for constitutional and environmental factors, we define populations with high risks of skin cancer in areas with varying UVB exposure. New estimates of dose-response according to cell type continue to show that the effect of increases in UVB would be greatest for squamous cell carcinomas, which would be twice as great as those for basal cell carcinomas, and four times as great for skin melanomas. Caucasians in the southern regions of the United States are twice as likely to develop skin cancer and melanoma in their lifetimes as those residing in northern regions. Preliminary studies indicate that a photosensitive, natural element found in human skin may be associated with increased skin cancer risk.